Sensor devices which are used, for example, in security systems of motor vehicles, usually have a chip structure having a sensor chip and an evaluation chip that is electrically connected to the sensor chip. The sensor chip is developed in the form of a micromechanical component (MEMS, microelectromechanical system), in order to record a physical measured quantity, such as an acceleration or a rotational rate. The evaluation chip is used for controlling the sensor chip and for the evaluation or further processing of measuring signals of the sensor chip.
Depending on their applications, the sensor devices may be developed undamped or damped. In one conventional specific embodiment, the chips are provided on a floor plate, which is situated within a frame-shaped housing base body (premold frame). The base plate is surrounded at its edge by an electric damper element, and connected on the inside to the housing frame by the damper element. In this way, the floor plate is deflectable with respect to the housing frame, whereby damping of the chip from outer mechanical influences, such as jolts or vibrations is made possible. The housing frame has contact elements, via which the sensor device is able to be contacted from the outside. Within the housing frame, the contact elements are electrically connected via bonding wires to the evaluation chip.
In the conventional sensor device, there may be the problem that the damping is effective only at certain frequencies, whereby vibrations are able to lead to interferences of the sensor chip and with that, of the measuring signals. The damping properties are a function of the geometry of the damper element and the material properties of the damper material (usually a silicone). Besides the required elasticity, however, the damper element is subject to further requirements, so that selection of the material is greatly restricted. It is required, for example, that the damper material be sprayable, in order to make simple processing possible, as well as good adhesion with regard to the floor plate (e.g., steel) and the housing frame (e.g., plastic). For the decoupling of various interference frequencies, it may be required for each case to have its own housing, which is connected with high expenditure.
Furthermore, the construction of the sensor device may lead to the impairment or interruption of the electrical connection. Jolts or accelerations, which may occur, for instance, during a drop test or improper handling of the sensor device, result in a relatively great deflection of the base plate with respect to the housing frame. This creates a corresponding relative motion in the bonding wires, which are fastened to the evaluation chip and at the housing frame. Connected with this is a drifting away of the bonding wires or tearing or loosening of the bonding wires from their contact locations. The essentially horizontal construction of the sensor device also has a relatively great lateral requirement for space. Also provided are dead areas in the form of sealing areas within the housing frame and around the base plate, by which the base area of the sensor (footprint) is clearly greater than that of the chip.
German Patent Application No. DE 10 2009 000 571.4 describes a further damped sensor device in which an electrical connection between contact elements of a housing frame and an evaluation chip is produced with the aid of a flexible printed-circuit board, in order to achieve a construction that is insensitive to jolts. In one specific embodiment, the flexible printed circuit board has a section used as the base part, on which the chip is situated. The base plate is surrounded at its edge by an electric damper element, and connected on the inside to the housing frame by the damper element.